You should be able to tell if the cable in the barrel adjuster goes to the brakes or the derailleur.
At this point, it may be reasonable to take it to a shop for adjustment. Likely to be cheaper than changing out crankset. They should at least be able to tell you if the rub is avoidable.
Your comment about redundant gearing is correct. I have a triple, I use the smallest chainring only on steep climbs, and only on the largest 3 (or sometimes 4 if I hit a short false flat) rear cogs. I find the middle ring useful for moderate climbs, or for variable terrain, but there is quite a bit of overlap with the large ring.